Wilamowski B.M., Irwin J.D. The Industrial Electronics Handbook. Second Edition: Industrial Communication Systems

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58-1

58.1 requirements for SCaDa Data Collection

in Electric Power and Other Industries

Electric.power.networks.consist.of.transmission.systems.and.distribution.systems.. e.transmission.

syst

.consi

sts

.of.high

-voltage

.powe

.line

.and.a.rela

tively

.smal

.numbe

.of.larg

.subs

tations.

.It.deli

vers

ener

.to.term

inal

.stat

ions

.wher

.tran

sformers

.step.the.volt

age

.down.and.feed.ener

.into.the.dist

ribu-

tion

.netw

ork.

.Dist

ribution

.netw

orks

.incl

ude

.larg

.numbe

.of.smal

ler

.subs

tations

.and.tran

sformers

.that.

furt

her

.conv

ert

.the.powe

.to.main

.volt

ages

.and.reti

culate

.this.to.dome

stic

.and.comm

ercial

.cons

umers.

Larg

.gene

ration

.stat

ions

.conn

ect

.dire

ctly

.to.the.tran

smission

.syst

.and.smal

ler

.gene

ration

.stat

ions

can.con

nect

.to.the.tra

nsmission

.or.dis

tribution

.net

works.

Modern

. subs

tations

. incl

ude

. equi

pment

. to. cont

rol

. and. prot

ect

. the. powe

. syst

em.

. ese. syst

ems

moni

tor

.many.quan

tities

.such.as.volt

ages,

.curr

ents,

.powe

.ows

.and.the.stat

.of.swit

ches

.and.othe

equi

pment.

.Some.devi

ces

.in.subs

tations

.perf

orm

.func

tions

.to.autom

atically

.disc

onnect

.powe

.on.the.

occu

rrence

.of.prob

lems

.such.as.over

loads,

.shor

.circ

uits,

.or.faul

.such.as.thos

.indu

ced

.by.elec

tri-

cal

.storm

. e.high

-voltage

.tran

smission

.subs

tations

.are.the.most.heav

ily

.moni

tored

.and.prot

ected

sites.with.lowe

.volt

age

.subs

tations

.and.dist

ribution

.syst

.equi

pment

.typi

cally

.rece

iving

.less.rigo

rous

moni

toring

.per.site.but.hav

ing

.a.muc

.lar

ger

.numb

.of.pla

.ite

.tha

.can.be.mon

itored.

Substations

.are.usua

lly

.moni

tored

.by.supe

rvisory

.cont

rol

.and.data.acqu

isition

.(SCA

DA)

.syst

ems.

 ese.syst

ems

.comm

unicate

.thei

.data.to.a.cont

rol

.cent

.wher

.the.info

rmation

.is.used.to.allo

.oper

at-

ing

.sta.to.remo

tely

.moni

tor

.and.cont

rol

.the.powe

.netw

ork.

. e.oper

ators

.perf

orm

.rout

ine

.swit

ching

of.pla

.to.bri

.it.into.and.out.of.ser

vice

.and.to.qui

ckly

.res

tore

.pow

.ae

.fau

lts.

.dyna

mic

.char

acteristics

.of.the.elec

tric

.powe

.netw

ork

.can.resu

.in.extr

emely

.rapi

.chan

ges

.of.

the.network.behavior.or.operation.in.response.to.any.changes.in.load,.the.availability.of.generation,.or.

dist

urbances.

. e.SCAD

.syst

.must.ther

efore

.prov

ide

.rapi

.upda

.of.the.moni

tored

.data.and.sup-

ort

.mini

mal

.dela

.in.issu

ing

.cont

rol

.comm

and

.requ

ests

.from.the.cont

rol

.cent

.to.the.eld.equi

pment.

 e.requ

ired

.resp

onsiveness

.(bei

.the.time.from.a.chan

.in.the.eld.occu

rring

.unti

.it.is.visib

.to.the.

oper

ator,

.or.time.for.a.requ

est

.from.the.oper

ator

.to.caus

.an.acti

.in.the.eld

)

.in.tran

smission

.netw

orks

is.typi

cally

.less.than.5.s..Beca

use

.of.this.rapi

.resp

onsiveness,

.elec

tric

.powe

.SCAD

.syst

ems

.are.oen.

consi

dered

.to.be.rea

l-time

.or.nea

r-real-time

.sys

tems.

DNP3 and IEC 60870-5

58.1. Requirements.for.SCADA.Data.Collection.in.Electric.

Powe

.and.Oth

.Ind

ustries...........................................................58-1

58.2

. Feat

ures

.Com

mon

.to.IEC.608

70-5

.and.DNP

Data.Typ

ing,

.Rep

ort

.by.Exc

eption,

.Err

.Rec

overy...................58-3

58.3

. Die

rentiation

.bet

ween

.IEC.608

70-5

.and.DNP

.Ope

rating

Phil

osophy,

.Mes

sage

.For

matting,

.Ec

iency,

.TCP

/IP

Tran

sport..........................................................................................58-5

References.....................................................................................................58-9

Andrew C. West

Invensys Operations

Mana

gement

58-2 Industrial Communication Systems

Power. system.control.requires.high.integrity.of.both. data.reporting.and.control.activation.. e.

ope

rator

.mus

.be.abl

.to.tru

.the.acc

uracy

.of.the.inf

ormation

.rep

orted

.to.the.con

trol

.cen

ter

.in.ord

.to.

qui

ckly

.ded

uce

.any.req

uired

.res

ponses.

. e.sys

tem

.mus

.cor

rectly

.res

pond

.to.any.ope

rator

.com

mand

and.onl

.act

ivate

.exa

ctly

.the.equ

ipment

.tha

.is.req

uested

.by.the.ope

rator:

.Ina

dvertent

.ope

ration

.of.oth

dev

ices

.can

not

.be.tole

rated

.and.con

stitutes

.a.saf

ety

.ris

.to.per

sonnel

.and.equ

ipment.

.If.any.asp

ect

.of.a.

con

trol

.com

mand

.fai

.a.val

idation

.ste

.the.com

mand

.is.dis

carded

.rat

her

.tha

.all

owing

.the.pos

sibility

of.in

correct

.ex

ecution

.of.a.co

mmand

.re

quest.

When

.fau

lts

.occu

.in.elec

tric

.pow

.sys

tems,

.aut

omated

.pro

tection

.equ

ipment

.ins

talled

.in.sub

stations

typ

ically

.act.to.ide

ntify

.the.fau

.and.tak

.mea

sures

.to.min

imize

.dam

age

.to.the.sys

tem.

. ey.tak

.act

ions

suc

.as.aut

omatically

.disc

onnecting

.or.isol

ating

.the.fau

lty

.secti

.of.the.net

work.

. e.act

ions

.of.thi

pro

tection

.equ

ipment

.are.rap

.and.are.tun

.by.car

efully

.eng

ineering

.a.com

plex

.set.of.par

ameters

.tha

aec

.the

.ope

ration.

.To.ver

ify

.the.cor

rect

.ope

ration

.of.thi

.equ

ipment

.and.to.fac

ilitate

.the.cor

rect

.tun

ing

of.the.par

ameters,

.the.exa

.tim

ing

.of.cha

nges

.of.the.dat

.bei

.mon

itored

.by.the.pro

tection

.equ

ipment

and.the.res

ponses

.of.the.pro

tection

.equ

ipment

.are.imp

ortant

.to.fac

ilitate

.the.pos

tmortem

.ana

lysis

.of.any.

fau

.and.the.cor

responding

.ope

ration

.of.the.equ

ipment.

. is.dat

.gat

hering

.req

uires

.accu

rate

.col

lection

of.the.tim

.of.the.cha

nges

.wit

.reso

lution

.in.the.ran

.fro

.mil

liseconds

.dow

.to.mic

roseconds

.and.can.

inv

olve

.cap

ture

.of.the.pow

.sys

tem

.wav

eforms

.for.vol

tage

.and.cur

rent

.at.vari

ous

.poi

nts

.in.the.sys

tem.

. e.

cor

relation

.of.dat

.col

lected

.fro

.di

erent

.pla

ces

.in.the.pow

.net

work

.req

uires

.clo

.syn

chronization

.of.

the.clo

cks

.used.to.tim

e-stamp

.the.dat

. e.rep

orting

.of.the.tim

e-stamped

.dat

.to.a.sys

tem

.tha

.arc

hives

this.information.is.sometimes.called.“sequence.of.events”.reporting.or.SOE.

Electric

.pow

.SCA

.sys

tems

.are.amo

.the.ear

liest

.app

lications

.for.wid

e-scale

.dis

tributed

.tel

eme-

try.

. e.pri

mary

.pla

.in.gen

eration

.sta

tions

.and.sub

stations

.has.a.lon

.ser

vice

.lif

.(ty

pically

.30.or.mor

yea

rs).

. e.ass

ociated

.con

trol

.equ

ipment

.and.com

munications

.sys

tems

.typ

ically

.hav

.com

mensurate,

tho

ugh

.sho

rter,

.lif

.spa

.in.the.ord

.of.10.yea

rs.

. us

.the

.are.man

.SCA

.sys

tems

.ope

rating

.ove

rel

atively

.old.com

munication

.sys

tems

.or.sys

tems

.wit

.old.arc

hitectures.

. es

.com

munication

.sys

tems

oe

.hav

.lim

ited

.ban

dwidth

.and.may.hav

.rel

atively

.hig

.err

.rat

.whe

.com

pared

.wit

.tho

.use

in.oth

.app

lications

.suc

.as.Inf

ormation

.Tec

hnology

.or.fac

tory

.auto

mation.

.Man

.ins

talled

.sys

tems

ope

rate

.ove

.ser

ial

.dat

.lin

.wit

.dat

.rat

.in.the.ran

.300

–9600

.bau

.Eve

.whe

.the.equ

ipment

.can.

be.upd

ated,

.it.is.not.alw

ays

.fea

sible

.to.sign

icantly

.mod

ify

.the.ava

ilable

.ban

dwidth

.wit

hout

.rep

lacing

the.ent

ire

.com

munication

.sys

tem.

.Whe

.upg

rades

.occ

ur,

.mod

ern

.net

working

.tec

hnologies

.are.som

times,

.but.not.alw

ays,

.ado

pted.

.For.som

.app

lications,

.tra

ditional

.ser

ial

.dat

.sys

tems

.are.mor

.ec

ient

or.mor

.cos

t-eective.

. is.can.be.esp

ecially

.the.cas

.whe

.it.is.nec

essary

.to.pro

vide

.acc

ess

.to.a.numb

of.e

.de

vices

.ov

.a.sh

ared

.me

dia

.su

.as.a.li

mited-bandwidth

.ra

dio

.ch

annel.

.req

uirements

.for.rap

.dat

.upd

ate

.and.lim

ited

.ban

dwidth

.ava

ilability

.dic

tate

.a.nee

.for.eci

ent

.uti

lization

.of.the.ava

ilable

.ban

dwidth.

. e.dat

.and.com

mand

.int

egrity

.req

uirements

.are.sat

ised

.by.mec

ha-

nisms

.tha

.ver

ify

.and.val

idate

.dat

.and.com

mands.

. e.acc

urate

.tim

e-stamping

.of.dat

.req

uires

.tha

.SOE.

inf

ormation

.mus

.be.sup

ported

.and.tha

.the

.is.a.mec

hanism

.to.acc

urately

.syn

chronize

.the.tim

.acr

oss

mul

tiple

.wid

ely

.dis

persed

.dev

ices.

.Som

.of.the

.req

uirements

.are.inh

erently

.con

tradictory

.(e.

g.,

.sho

lat

ency

.and.low.ban

dwidth)

.and.con

sequently

.a.com

promise

.mus

.be.ach

ieved

.whe

.add

ressing

.the

Traditionally,

.the

.nee

.wer

.met.by.ven

dors

.pro

viding

.a.var

iety

.of.pro

prietary

.pro

tocols

.and.com

munication

.int

erfaces

.tha

.spe

cically

.add

ress

.the

.req

uirements.

.In.mor

.rec

ent

.tim

es,

.a.numb

.of.

ope

.st

andards

.ha

.be

.de

veloped

.an

.wi

dely

.ad

opted

.fo

.th

.pu

rpose.

Modern

. SCA

. sys

tems

. alm

ost

. uni

versally

. ado

. sta

ndard

. int

erfaces

. fro

. the. tel

ecommunication

ind

ustries

.suc

.as.V.2

4/V.28

.(RS

-232)

.or.V.1

.(RS

-422/RS-485)

.int

erfaces

.for.ser

ial

.or.mod

.int

erfaces

.and.

any.of.the.IEE

.802.int

erfaces

.for.Eth

ernet

.(us

ually

.TCP

/IP),

.wit

.100

BaseT

.and.100

BaseFX

.now.bei

.com

mon.

. es

.int

erfaces

.are.use

.wit

.SCA

DA-specic

.pro

tocols:

.In.the.ele

ctric

.pow

.ind

ustry,

.the.mos

.com

monly

.use

.SCA

.pro

tocols

.are.IEC.608

70-5-101

.or.IEC.608

70-5-104

.(do

minant

.in.Eur

ope)

.and.DNP

(co

mmon

.in.Eng

lish-speaking

.cou

ntries).

. es

.two.fam

ilies

.of.pro

tocols

.are.des

cribed

.fur

ther

.bel

ow.

Some

.oth

.ind

ustries

.(e.

g.,

.rai

.tra

nsportation)

.hav

.sim

ilar

.req

uirements

.for.SCA

.to.tho

fou

.in.the.ele

ctric

.pow

.ind

ustry

.(e.

g.,

.tra

ction

.pow

.con

trol)

.and. ado

.the.sam

.SCA

DNP3 and IEC 60870-5 58-3

protocol.standards.for.those.applications,.but.will.adopt.different.standards.for.other.applications.

(e.g

.for.safe

.inte

rfaces

.such.as.sign

aling).

Other

.major.indu

stries

.with.larg

e-scale

.wide

.dist

ributed

.SCAD

.netw

orks

.incl

ude

.oil.and.gas.pipe

line

.moni

toring

.and.wate

.and.wast

ewater

.moni

toring.

. ese.indu

stries

.have.some.requ

irements

.in.

comm

.wit

.ele

ctric

.pow

.SCA

.and.som

.di

erences.

.oil.and.gas.indu

stries

.and.wate

.and.wast

ewater

.indu

stries

.typi

cally

.have.a.rela

tively

.long.time.

doma

.asso

ciated

.with.thei

.moni

toring

.requ

irements:

.Pres

sures

.in.gas.pipe

lines

.and.rate

.of.ow.and.

leve

.for.liqu

ids

.gene

rally

.do.not.chan

.rapi

dly

.or.need.prom

.atte

ntion.

. is.gene

rally

.allo

.for.a.

slow

.data.coll

ection

.stra

tegy

.with.a.peri

.of.data.coll

ection

.in.the.rang

.from.minu

tes

.to.hour

.oen.

bein

.acce

ptable.

.One.nota

ble

.exce

ption

.to.this.is.the.prom

.repo

rting

.of.“urg

ent”

.alar

.cond

itions

that.mig

.nec

essitate

.ope

rator

.int

ervention

.or.mai

ntenance

.cal

.out

For

.thes

.pipe

line

.indu

stries,

.ther

.are.few.addi

tional

.requ

irements

.that.are.not.cove

red

.by.powe

.syst

appl

ications

.and.ther

efore

.the.elec

tric

.powe

.prot

ocols

.and.also.Modb

.(whe

.no.time.taggi

.or.SOE.data.

is.requ

ired)

.are.appl

icable.

.Prop

rietary

.prot

ocols

.are.also.stil

.very.comm

.in.the.oil.and.gas.indu

stries.

In.rece

.year

.the.wate

.indu

stries

.in.the.Unit

.King

dom

.and.Aust

ralia

.have.stan

dardized

.on.DNP3.for.

SCAD

.inte

rfaces

.and.are.maki

.use.of.the.SOE.func

tionality

.to.allo

.accu

rate

.reco

rding

.of.eld.acti

ons

whil

.allo

wing

.infr

equent

.poll

ing.

.DNP3.supp

orts

.an.unso

licited

.repo

rting

.mech

anism

.wher

.chan

ges

.can.

be.repo

rted

.from.the.eld.with

out

.need

ing

.a.requ

est

.from.the.mast

.stat

ion.

. e.use.of.this.feat

ure

.allo

prom

.indi

cation

.of.urge

.alar

.cond

itions

.with

out

.requ

iring

.freq

uent

.poll

ing

.of.each.remo

.site

.IEC.60870.series.proles.have.not.been.widely.adopted.in.the.oil.and.gas.and.water.industries,.

possi

bly

.bec

ause

.of.a.per

ception

.tha

.the

.are.pow

er-system

.spe

cic.

58.2 Features Common to IEC 60870-5 and DNP3: Data

typin

repor

t by Exception, Error

recov

ery

 e.International.Electrotechnical.Commission’s.60870-5.series.of.standards.were.developed.by.the.

IEC.Tech

nical

.Comm

ittee

.57.over.the.peri

.1988

–2000.

.Some.part

.have.been.upda

ted

.with.subs

quent

.revi

sions

.and.exte

nsions.

. is.seri

.incl

udes

.the.IEC.6087

0-5-101

.[1].and.6087

0-5-104

.[2].pro

les

for.basic.tele

control

.task

.over.seri

.and.TCP/

.link

. e.IEC.6087

0-5

.seri

.are.reco

gnized

.as.the.

inte

rnational

.stan

dards

.for.elec

tric

.powe

.SCAD

.tran

smission

.proto

cols.

. eir.use.for.that.purp

ose

.is.

mand

ated

.in.many.coun

tries

.by.gove

rnment

.legi

slation

.and.they.are.wide

.adopt

.in.Euro

.and.in.

coun

tries

.whe

.Eur

opean

.com

panies

.and.con

ventions

.hav

.sign

icant

.in

uence.

IEC

.6087

.part

.-5-1.thro

ugh

.to.-5-5.den

.a.“coo

kbook”

.of.rule

.for.spec

ifying

.SCAD

.Tele

control

proto

cols.

.Part.-5-1

.(som

etimes

.also.know

.as.“Tel

econtrol

.101”.or.“T10

1”)

.spec

ies

.a.full

.den

pro

.for.basic.Tele

control

.task

.base

.on.thes

.rule

.T101.incl

udes

.the.den

ition

.of.gene

ral-purpose

and.powe

r-system-specic

.data.objec

.and.func

tions

.dire

ctly

.appl

icable

.to.the.subs

tation

.to.cont

rol

cent

.SCAD

.link

.Part.-5-1

.(“T1

04”)

.den

.the.tran

smission

.of.T101.over.TCP/

.with.some.

mino

.fun

ctional

.ext

ensions

.suc

.as.the.add

ition

.of.tim

.tag

.to.con

trol

.obje

cts.

DNP3

.[3].is.a.gene

ral-purpose

.SCAD

.proto

col

.base

.on.the.desig

.rule

.in.the.earl

.part

.of.IEC.

6087

.that.adds.some.conc

epts

.that.are.quit

.die

rent

.from.thos

.den

.in.late

.part

.of.IEC.6087

0-5.

It.den

.data.type

.and.func

tions

.for.the.tran

smission

.of.gene

ric

.SCAD

.data

.Whil

.it.was.desig

ned

for.pow

.sys

tem

.app

lication,

.it.doe

.not.inc

lude

.pow

er-system-specic

.dat

.obje

cts.

DNP3

.was.init

ially

.deve

loped

.by.the.Cana

dian

.SCAD

.comp

any

.West

ronic

.and.was.plac

.in.the.publ

doma

.in.1993

.It.is.now.main

tained

.by.an.inde

pendent

.body.calle

.the.DNP.User

.Grou

.and.is.cons

idered

a.de.facto.standard.for.electric.power.SCADA.communication.in.North.America.where.it.is.used.by.over.80%.

of.powe

.util

ities

.[4]..DNP3.is.also.the.de.fact

.stan

dard

.for.elec

tric

.powe

.SCAD

.comm

unications

.in.most.

othe

.Engl

ish-speaking

.coun

tries

.and.plac

.wher

.Nort

.Amer

ican

.vend

ors

.have.sign

icant

.mark

.inu

ence.

 e.crea

tion

.of.DNP3.appe

ars

.to.have.been.inu

enced

.by.a.prag

matic

.resp

onse

.to.util

ity

.mark

.dema

nds

.for.

conf

ormance

.to.the.IEC.6087

.stan

dard

.in.the.year

.prio

.to.the.publ

ication

.of.IEC.6087

0-5-101.

.Its.plac

ement

58-4 Industrial Communication Systems

in.the.market.as.an.open.standard.promoted.its.adoption.and.it.has.

now.bee

.rat

ied

.as.IEE

.Sta

ndard

.181

The

.her

itage

.of.the.pro

tocols

.and. the. dep

endencies

.in. the.

doc

umentation

.are.ill

ustrated

.in.Fig

ure

.58.

.ele

ments

.tha

.are.com

mon

.to.bot

.IEC.608

70-5-101/-104

and.DN

.in

clude

.th

.fo

llowing:

•

. T10

1/T104

. and. DNP

. ado

. the. “En

hanced

. Per

formance

Arc

hitecture”

.(EPA

)

.ref

erence

.mod

.desc

ribed

.in.IEC.608

70-

5-3

.tha

.uses.onl

.the.Phy

sical,

.Dat

.Lin

.and.App

lication

lay

ers

.of.the.ISO.7-L

ayer

.ref

erence

.mod

.and.dis

penses

.wit

the. Net

work,

. Tra

nsport,

. Ses

sion

. and. Prese

ntation

. lay

ers.

DNP

.the

.ext

ends

.the.EPA.mod

.wit

.a.tra

nsport

.“fu

nc-

tion”

. (a. pseu

do-layer)

. tha

. per

mits

. asse

mbly

. of. mes

sages

lar

ger

.tha

.a.sin

gle

.dat

.lin

.fra

me.

•

. T10

.and.DNP

.use.dat

.lin

.fra

.for

mats

.and.dat

.lin

.fra

.han

dling

.rul

.de

ned

.in.IEC.6087

5-1

.and.IEC.6087

0-5-2.

. es

.pro

vide

.for.goo

.mes

sage

.ec

iency

.wit

.goo

.err

.det

ection

.and.

rej

ection,

.mee

ting

.the.bas

.ele

ctric

.pow

.SCA

.req

uirements

.for.mes

sage

.int

egrity

.and.ec

iency.

•

. T10

1/T104

.and.DNP

.are.bas

.on.the.“Re

port

.by.Exc

eption”

.(or.RBE

)

.par

adigm

.whe

re,

.in.nor

mal

.operation,.only.changes.are.reported.and.data.that.has.not.changed.is.not.reported.. is.meets.

the.basi

.ele

ctric

.pow

.SCA

.req

uirement

.for.ec

iency

.of.mes

sage

.rep

orting

.(by.eli

minating

the.unn

ecessary

.rep

orting

.of.unc

hanged

.dat

.and.als

.add

resses

.the.req

uirements

.to.ret

urn

.SOE.

inf

ormation

.(ch

anges

.sen

.in.seq

uence

.and.wit

.tim

e-stamping).

. e.RBE.mec

hanism

.req

uires

the.ini

tial

.col

lection

.of.all.dat

.fro

.a.el

.dev

ice

.thr

ough

.an.“in

tegrity

.pol

l”

.and.the.sub

sequent

rep

orting

.of.all.cha

nges

.in.the.cor

rect

.chr

onological

.tim

.seq

uence.

.If.thi

.is.don

.cor

rectly

.wit

no.lo

.of.SO

.da

ta,

.th

.re

sulting

.da

.im

age

.in.th

.re

ceiving

.st

ation

.is.al

ways

.co

rrect.

•

. Con

trol

.com

mand

.pro

cedures

.inc

lude

.a.“Se

lect

.Bef

ore

.Ope

rate”

.or.“Se

lect/Execute”

.mech

anism

also.cal

led

.a.“tw

o-pass

.con

trol.”

. is.mech

anism

.pro

vides

.con

trol

.com

mands

.wit

.sig

nicantly

enh

anced

.sec

urity

.aga

inst

.ran

dom

.dat

.err

ors

.int

roduced,

.for.exa

mple,

.by.ind

uced

.noi

.int

erference

in.the.com

munication

.sys

tem.

. is.sup

ports

.the.ele

ctric

.pow

.SCA

.req

uirement

.for.hig

int

egrity

.vali

dation

.of.con

trol

.com

mands.

•

. Dat

.obje

cts

.inc

lude

.qua

lity

.ag

.tha

.pro

vide

.ext

.inf

ormation

.to.qua

lify

.or.val

idate

.the.dat

tha

.is.be

ing

.re

ported.

•

. Tim

.st

amps

.on.ch

ange

.da

.th

.in

dicate

.th

.ti

.of.me

asurement

.of.th

.re

ported

.da

ta.

•

. Dat

.an

.fu

nction

.ty

pes

.su

pported

.by.bo

.IE

.60

870-5-101/-104

.an

.DN

.in

clude

•

. Rep

orting

.of.sin

gle-bit

.bi

nary

.st

atus

.ob

jects

•

. Rep

orting

.of.do

uble-bit

.bi

nary

.st

atus

.ob

jects

•

. Rep

orting

.of.in

teger

.an

alog

.me

asurands

•

. Rep

orting

.of.o

ating-point

.an

alog

.me

asurands

•

. Rep

orting

.of.co

unters

.(a

lso

.ca

lled

.ac

cumulators

.or.in

tegrated

.tot

als)

•

. Con

trol

.co

mmands

.to.bi

nary

.ou

tputs

.(o

n/o

.or.tr

ip/close

.co

mmands)

•

. Con

trol

.co

mmands

.to.in

teger

.or.o

ating-point

.se

tpoint

.ou

tputs

•

. Con

trol

.co

mmands

.to.fr

eeze

.co

unters/accumulators

•

. Abi

lity

.to.re

.an

.wr

ite

.l

.to.or.fr

.e

.de

vices

•

. Abi

lity

.to.set.the.tim

.and.dat

.(cl

ock

.and.cal

endar)

.in.the.el

.dev

ices,

.inc

luding

.cor

rect-

ing

.fo

.th

.co

mmunication

.sy

stem

.pr

opagation

.de

lay

•

. Abi

lity

.to.re

set

.re

mote

.de

vices

•

. Com

mands

.to.per

form

.an.“in

tegrity

.pol

l”

.(co

llect

.a.ref

reshed

.dat

.ima

.of.all.dat

.fro

a.e

.de

vice)

•

. Com

mands

.to.co

llect

.sp

ecic

.su

bsets

.of.da

.fr

.a.e

.de

vice

IEC 60870-5-1

IEC 60870-5-2

DNP3 IEC 60870-5-4

IEC 60870-5-101

IEC 60870-5-104

IEC 60870-5-3

IEC 60870-5-5

FIGURE 58.1 Dependencies. of. the.

spe

cications.

DNP3 and IEC 60870-5 58-5

•. Optional.modes.of.operation.where.the.eld.device.can.report.change.data.without.being.polled.

by.the.mas

ter

.sta

tion.

•

. Test.pro

cedures

.to.ver

ify

.the.cor

rect

.ope

ration

.of.a.pro

tocol

.imp

lementation

.in.a.dev

ice.

•

. To.supp

ort

.SOE.func

tionality,

.devi

ces

.inco

rporate

.even

.data.bue

rs.

. e.prot

ocols

.den

.mecha

nisms

.to.veri

.the.corr

ect

.repo

rting

.of.the.data.from.these.bue

rs:

. is.data.can.be.repe

ated

.if.nec-

sary

.to.ensu

.that.it.is.corr

ectly

.repo

rted.

.Once.veri

ed,

.it.can.be.clea

red

.from.the.even

.bue

rs.

•

. T104.and.DNP3.have.stan

dardized

.XML.le.den

itions

.for.mapp

ing

.betw

een

.thei

.stan

dard

.data.

objec

.and.data.attr

ibutes

.of.the.Logi

cal

.Node.objec

.den

.in.the.subs

tation

.autom

ation

.stan

dard

.IEC.618

50.

.T10

.can.als

.mak

.use.of.the.T10

.map

ping

.pro

cess.

•

. DNP3.has.a.secu

.auth

entication

.proc

edure

.that.is.base

.on.IEC.6235

1-5.

. e.equi

valent

.func

tionality

.for.T10

.and.T10

.is.und

.dev

elopment

.at.the.tim

.of.wri

ting.

Any

.devi

.that.impl

ements

.thes

.proto

cols

.can.choo

.to.impl

ement

.only.thos

.part

.of.the.proto

col

(data.objects.and.functions).needed.to.support.the.operation.of.that.device..Each.protocol.has.some.

mand

atory

.“ho

usekeeping”

.fun

ctionality

.tha

.mus

.be.imp

lemented.

58.3 Differentiation between IEC 60870-5andDNP3

Operating Philosophy, Message Formatting,

Efficiency,

tCP/I

transp

ort

While.T101,.T104,.and.DNP3.share.many.common.operational.characteristics.such.as.the.use.of.RBE,.

ther

.are.some.deta

.die

rences

.in.oper

ating

.phil

osophy

.betw

een

.the.IEC.6087

0-5

.proto

cols

.and.DNP3

 ese.die

rences

.are.evid

ent

.in.the.data.objec

.and.mess

age

.form

ats

.and.in.the.comm

and

.sequ

ences

used.to.man

ipulate

.the

.some.case

.the.IEC.6087

.and.DNP3.prot

ocol

.desc

riptions

.empl

.die

ring

.term

inology

.to.

desc

ribe

.the.same.thin

.and.simi

lar

.term

inology

.to.desc

ribe

.die

rent

.thin

gs.

. is.easi

.lead

.to.

conf

usion,

.espe

cially

.for.peop

.conv

ersant

.with.the.deta

ils

.of.one.prot

ocol

.who.have.rela

tively

.supe

cial

.cont

act

.with.the.othe

.In.such.case

.the.exis

ting

.fami

liarity

.with.one.prot

ocol

.read

ily

.lead

.to.

misu

nderstanding

.or.inco

rrect

.impl

ementation

.of.the.othe

.Care

ful

.read

ing

.of.both.sets.of.spec

ica-

tions

.can.be.nece

ssary

.in.orde

.to.clea

rly

.unde

rstand

.the.simi

larities

.and.dist

inctions

.of.the.prot

ocols.

Some

times,

.the.end.user

.also.need.to.be.awar

.of.thes

.deta

ils

.in.orde

.to.corr

ectly

.sele

.con

gura-

tion

.opti

ons,

.etc.

.exam

ple

.of.die

ring

.term

inology:

. e.mast

.stat

ion

.equi

pment

.typi

cally

.foun

.in.a.SCAD

cont

rol

.cent

.is.call

.a.“con

trolling

.stat

ion”

.in.IEC.6087

.and.a.“mas

ter”

.in.DNP3

;

.the.subs

tation

equi

pment

.such.as.a.remo

.term

inal

.unit.(RTU

)

.that.repo

rts

.subs

tation

.data.to.the.cont

rol

.cent

.is.

call

.a.“con

trolled

.sta

tion”

.in.IEC.608

.and.an.“ou

tstation”

.in.DNP

.exam

ple

.of.the.same.terms.mean

ing

.somew

hat

.die

rent

.thin

.exis

.in.the.use.of.data.clas

ses.

.In.

IEC.6087

0-5,

.ther

.are.two.data.clas

ses

.used.for.poll

ing

.data.when.usin

.the.unba

lanced

.data.link.proc

dures,

.loose

.corr

esponding

.to.high.prio

rity

.(typ

ically

.even

.data

)

.in.Clas

.1.and.low.prio

rity

.(typ

ically

cyclic.analog.measurements).in.Class.2..In.DNP3,.there.are.four.classes:.Class.0.for.reporting.“Static.Data,”.

mean

ing

.the.curr

ent

.value.of.all.kind

.of.data

;

.and.Clas

ses

.1,.2,.and.3.that.are.thre

.separ

ate

.prio

rity

grou

.for.even

.data

. e.mecha

nisms

.for.decid

ing

.whic

.clas

.to.read.are.die

rent

.in.the.two.prot

ocols.

.prin

cipal

.tene

.of.the.IEC.60870

-5

.seri

.prot

ocols

.is.that.the.cont

rolled

.stat

ion

.in.the.subs

tation

shou

.dete

rmine

.what.data.is.to.be.sent.to.the.cont

rolling

.stat

ion

.(mas

ter

.stat

ion).

.In.the.bala

nced

.mode.

of.oper

ation,

.the.cont

rolled

.stat

ion

.simp

.tran

smits

.what

ever

.data.it.wish

.at.what

ever

.time.it.wish

es.

. e.

cont

rolling

.stat

ion

.simp

.ackn

owledges

.rece

ipt

.of.the.data.and.issu

.cont

rol

.comm

ands

.when.requ

ired.

.In.

the.unba

lanced

.mode.of.oper

ation,

.the.cont

rolled

.stat

ion

.acts.in.a.simi

lar

.mann

er,

.but.must.wait.for.a.poll.

requ

est

.(ee

ctively

.an.“inv

itation

.to.tran

smit”)

.from.the.cont

rolling

.stat

ion,

.to.whic

.it.resp

onds

.by.send

ing

.a.sing

.mess

age.

. e.cont

rolling

.stat

ion

.has.litt

.cont

rol

.over.what.the.cont

rolled

.stat

ion

.will.tran

smit,

othe

.than.bein

.able.to.requ

est

.“Cla

.1”.or.“Cla

.2”.data

.Norm

ally

.the.cont

rolling

.stat

ion

.requ

ests

.Clas

s2

58-6 Industrial Communication Systems

(low.priority,.usually.cyclic.data).unless.the.previous.response.indicates.that.there.is.high-priority.data.

ava

ilable

.(by.set

ting

.the.acc

ess

.dem

and

.ag)

.in.whi

.cas

.the.con

trolling

.sta

tion

.req

uests

.Cla

.1.dat

.In.

thi

.man

ner,

.the.con

trolled

.sta

tion

.is.fun

damentally

.in.con

trol

.of.the.cor

rect

.seq

uence

.of.rep

orting

.of.dat

to.the.con

trolled

.sta

tion.

.In.DNP

.the.out

station

.alw

ays

.rep

lies

.wit

.exa

ctly

.the.dat

.tha

.the.mas

ter

.has.

req

uested:

. e.mas

ter

.has.ful

.con

trol

.ove

.wha

.wil

.be.sen

.In.ord

.for.the.cor

rect

.dat

.rep

orting

.to.be.

pre

served

.in.DNP

.the.mas

ter

.mus

.onl

.req

uest

.sta

tic

.dat

.(th

.cur

rent

.val

.of.inp

uts)

.if.it.is.als

.req

uest-

ing

.all.bu

ered

.even

.for.tho

.sam

.inp

uts

.in.the.sam

.req

uest.

. is.is.cri

tical

.for.cor

rect

.dat

.rep

orting.

Note:

.In.al

.th

.pr

otocols,

.an.un

derstanding

.of.th

.un

derlying

.ph

ilosophy

.is.re

quired

.wh

.im

plement-

ing

.the.pro

tocol.

.It.is.pos

sible

.to.poo

rly

.imp

lement

.T10

.unb

alanced

.in.a.con

trolled

.sta

tion

.so.tha

.the.

critical.requirement.to.report.all.measurements.in.the.order.that.they.are.measured.is.violated.by.arcane.

con

guration

.set

tings.

.Sim

ilarly,

.it.is.pos

sible

.to.vio

late

.thi

.sam

.req

uirement

.in.a.DNP

.mas

ter

.by.not.

req

uesting

.bu

ered

.ev

ents

.wh

.st

atic

.da

.is.re

quested.

Dierentiators

.be

tween

.IE

.60

870-5-101/-104

.an

.DN

.ar

•

. e.T10

.pro

le

.is.str

ictly

.for.use.ove

.ser

ial

.lin

ks,

.T10

.is.str

ictly

.for.use.ove

.TCP

/IP

.tra

nsports.

 e.dat

.lin

.fra

.(IE

.608

70-5-1

.FT1

.2)

.de

ned

.for.T10

.is.rep

laced

.by.a.cut

-down

.fra

.for.

T10

.toge

ther

.wit

.di

erent

.mes

sage

.con

rmation

.rul

es.

.T10

.is.per

mitted

.to.use.unb

alanced

dat

.lin

.ser

vices

.(re

quired

.for.use.on.mul

ti-drop

.cha

nnels)

.or.bal

anced

.dat

.lin

.ser

vices

.(re

quir-

ing

.a.ded

icated

.ful

l-duplex

.poi

nt-to-point

.lin

.bet

ween

.pai

.of.dev

ices).

. e.ope

ration

.of.T10

.is.

basically.the.same.as.the.operation.of.T101.over.balanced.data.links.with.the.dierentiation.that.a.

con

gurable

.numb

.of.T10

.inf

ormation

.mes

sages

.(I-

frames)

.can.be.sen

.bef

ore

.a.con

rmation

is.rec

eived,

.whe

reas

.the.T10

.rul

.req

uire

.a.con

rmation

.of.eac

.ind

ividual

.fra

me.

.DNP

.alw

ays

use

.the.ser

ial

.dat

.lin

.fra

.(ba

sed

.on.IEC.608

70-5-1

.FT3

)

.and.“ba

lanced

.tra

nsmission”

.rul

mod

ied

.to.all

.mul

ti-drop

.ope

ration

.on.hal

f-duplex

.cha

nnels.

.Whe

.DNP

.is.use

.wit

.TCP

.or.UDP

/IP,

.the.ser

ial

.dat

.lin

.fra

.is.enc

apsulated

.in.a.TCP.or.UDP.pac

ket.

. is.pro

cess

simp

lies

.the.so

ware

.for.fra

.han

dling

.(sa

.for.ser

ial

.or.IP).and.als

.simp

lies

.the.use.of.

DNP

.wit

.ter

minal

.ser

ver

.typ

.int

erfaces

.tha

.simp

.wra

.or.unw

rap

.the.ser

ial

.mes

sage

.wit

hin

the.TC

P/IP

.fr

ames

.an

.do.no

.ne

.to.ap

ply

.a.ne

.se

rial

.da

.li

.fr

ame.

•

. T10

1/T104

.mes

sages

.can.onl

.con

tain

.a.sing

.typ

.of.dat

.(e.

g.,

.sing

le-bit

.bin

ary

.inp

uts

.or.int

eger

ana

log

.mea

surands).

.DNP

.mes

sages

.can.con

tain

.mul

tiple

.typ

.of.dat

.in.one.mes

sage,

.as.lon

as.the.sam

.“fu

nction”

.(e.

g.,

.rea

.con

trol

.com

mand,

.rep

ort

.res

ponse,

.etc

.app

lies

.to.all.dat

.in.

the.mes

sage.

.Bec

ause

.of.thi

.the.res

ponse

.to.a.com

mand

.suc

.as.an.int

egrity

.pol

.can.con

sist

.of.

sev

eral

.sma

ller

.mes

sages

.in.T10

.or.T10

.and.a.sma

.numb

.of.lar

.mes

sages

.in.DNP

. is.

can.ae

.the.ec

iency

.of.rep

orting

.the.di

erent

.pro

tocols,

.esp

ecially

.ove

.dat

.lin

.wit

.spe

cial

pro

perties

.suc

.as.dat

.rad

ios

.(tu

rn-around

.tim

.may.be.lon

.com

pared

.to.tra

nsmit

.tim

.and.

sat

ellite

.li

nks

.(p

.pe

.by

te:

.Mo

.pa

ckets

.=.mo

.ov

erhead

.=.mo

.co

st).

•

. T10

1/T104

.mes

sages

.are.lim

ited

.to.the.max

imum

.size.of.a.sing

.dat

.lin

.fra

me.

. is.typ

ically

all

ows

.abo

.250.byt

.of.dat

.per.mes

sage.

.DNP

.mes

sages

.hav

.no.log

ical

.size.lim

it:

.DNP

.use

a.tra

nsport

.fun

ction

.and.app

lication

.lay

.fra

gmentation

.to.bui

.mes

sages

.of.any.len

gth

.and.

tra

nsmit

.the

.as.a.ser

ies

.of.app

lication

.fra

gments

.(ty

pically

.204

.byt

.in.size

)

.spl

.into.man

tra

nsport

.se

gments

.in.or

der

.to.t.th

.da

.li

.fr

ames.

•

. DNP

.use

.an.exp

licit

.app

lication

.con

rmation

.mec

hanism

.to.ver

ify

.rep

orting

.of.app

lication

dat

.T10

.ded

uces

.cor

rect

.app

lication

.rep

orting

.by.rel

iance

.on.dat

.lin

.con

rmation

.of.eac

lin

.fra

.or.togg

ling

.of.a.sing

.seq

uence

.numb

.bit.(kn

own

.as.the.Fra

.Cou

.Bit.or.FCB

)

.in.

a.sub

sequent

.req

uest.

.T10

.rel

ies

.on.the.con

rmation

.of.a.numb

.of.tra

nsmitted

.mes

sages.

. e.

max

imum

.win

dow

.size.in.T10

.is.con

gurable

.(pa

rameter

.k).but.is.typ

ically

.set.to.12..DNP

.als

permits.the.use.of.the.IEC.data.link.conrm.(except.on.TCP/IP.links),.however,.the.use.of.this.

pro

vides

.no.fu

nctional

.be

net

.an

.is.no

.re

commended.

•

. With

.a.dev

ice,

.T10

.and.T10

.mod

.eve

.kin

.of.dat

.as.bei

.a.memb

.of.a.sing

.set.of.

obje

cts,

.ide

ntied

.by.the.inf

ormation

.obje

.add

ress

.(IO

.of.the.dat

.ele

ment.

. e.IOA.val

ues

DNP3 and IEC 60870-5 58-7

may.be.sparsely.assigned.anywhere.in.the.allowed.range.(which.can.vary.depending.on.system-

wide

.par

ameters

.tha

.spe

cify

.the.IOA.size.and.how.it.is.for

matted).

.DNP

.mod

els

.all.dat

.wit

hin

a.dev

ice

.as.a.set.of.one

-dimensional

.arr

ays

.wit

.a.sep

arate

.arr

.for.eac

.typ

.of.dat

.Eac

.dat

ele

ment

.is.ide

ntied

.in.its.arr

.by.an.ind

.numb

er,

.sta

rting

.at.zer

.for.the.rs

.ele

ment.

.In.eac

pro

tocol,

.max

imum

.mes

sage

.rep

orting

.ec

iency

.is.ach

ieved

.if.the.IOA.ran

.or.ind

.numb

ran

.for.any.sing

.dat

.typ

.is.a.sing

.con

tiguous

.ser

ies

.wit

.no.gap

.For.T10

1/T104,

.thi

mea

.assi

gning

.IOA.val

ues

.X.to.X + n −.1.for.n.obje

cts

.of.the.sam

.typ

.and.for.DNP

.it.mea

assi

gning

.ind

ices

.0.to.n.−.1.for.n.obje

cts

.of.the.sam

.typ

.In.thi

.reg

ard,

.the.IEC.dat

.mod

som

ewhat

.re

sembles

.th

.re

gister

.ma

pping

.co

ncept

.us

.in.Mo

dbus.

•

. e.ide

ntication

.of.dat

.in.a.T10

.or.T10

.sys

tem

.is.by.the.uni

que

.comb

ination

.of.the.dev

ice

ide

ntity

.(ca

lled

.the.com

mon

.add

ress

.of.ASD

.or.CAA

)

.and.IOA.of.eac

.dat

.ele

ment

.in.the.

dev

ice.

. is.ide

ntication

.is.ind

ependent

.of.the.dat

.lin

.add

ress

.(in.T10

.or.the.IP.add

ress

.(in.

T10

.of.the.dev

ice

.rep

orting

.the.dat

.Eac

.di

erent

.dat

.obje

.in.a.T10

1/T104

.dev

ice

.(th

.dev

ice

hav

ing

.one.CAA.val

ue)

.mus

.hav

.a.di

erent

.IOA

.In.DNP

.the.comb

ination

.of.the.ser

ial

.cha

nnel

(or.IP.add

ress)

.of.the.dev

ice,

.the.DNP.add

ress

.of.the.dev

ice,

.the.dat

.typ

.and.the.obje

.ind

toge

ther

.un

iquely

.id

entify

.th

.da

.ob

ject.

•

. Bec

ause

.the.IEC.mes

sages

.can.onl

.rep

ort

.a.sing

.kin

.of.dat

.or.fun

ction

.in.a.sing

.mes

sage,

.the.

res

ponse

.to.som

.app

lication

.fun

ctions

.con

sist

.of.a.ser

ies

.of.mes

sages

.sta

rting

.wit

.a.“be

gin

.com

mand

.seq

uence”

.or.act

ivation

.con

rmation

.mes

sage

.(AC

TCON)

.fol

lowed

.by.one.or.mor

.dat

messages.and.terminating.with.an.“end.command.sequence”.or.activation.termination.message.

(AC

TTERM).

.In.DNP

.the.sam

.fun

ctionality

.typ

ically

.onl

.req

uires

.a.sing

.res

ponse

.mes

sage.

•

. e.T10

.and.T10

.mes

sages

.inc

lude

.a.“ca

use

.of.tra

nsmission”

.(CO

.val

.tha

.ser

ves

.to.assi

wit

.the.con

trol

.of.the.mul

tiple

.ste

.of.the.res

ponse

.to.a.com

mand

.and.is.par

tly

.use

ful

.for.ind

cating

.why.dat

.is.bei

.sen

.For.exa

mple,

.the.COT.can.di

erentiate

.bet

ween

.a.cha

nge

.tha

.has.

occ

urred

.spo

ntaneously

.(e.

g.,

.cir

cuit

.bre

aker

.tri

.due.to.pro

tection

.act

ion)

.or.bec

ause

.an.ope

rator

has.iss

ued

.a.con

trol

.com

mand

.to.cau

.the.cha

nge.

. is.inf

ormation

.can.be.add

.to.the.rel

evant

eve

.log.ent

ries.

.DNP

.doe

.not.inc

lude

.thi

.kin

.of.inf

ormation

.and.doe

.not.ind

icate

.why.a.

cha

nge

.oc

curred,

.me

rely

.th

.a.ch

ange

.ha

.oc

curred.

•

. DNP

.de

nes

.gen

eric

.SCA

.dat

.obje

cts

.(e.

g.,

.bin

ary

.inp

ut,

.set

point

.out

put)

.wit

hout

.assi

gn-

ing

.spe

cic

.mea

ning

.to.tho

.obje

cts.

.In.add

ition

.to.the

.basi

.typ

es,

.T10

.and.T10

.de

a.numb

.of.pow

er-system-specic

.obje

cts

.suc

.as.“st

.posi

tion

.inf

ormation”

.rep

resenting

.a.

tra

nsformer

.tap.numb

er,

.pro

tection

.eve

nts,

.pac

ked

.pro

tection

.sta

.eve

nts,

.and.pac

ked

.pro

tection

cir

cuit

.in

formation.

•

. DNP

.de

nes

.som

.com

plex

.gen

eric

.dat

.obj

ects

.suc

.as.“Oc

tet

.Str

ing”

.obj

ects

.and.“Da

.Set

”

.obj

ects

tha

.can.be.de

ned

.to.pro

vide

.fun

ctions

.suc

.as.mul

ti-byte

.var

iable

.val

ues

.or.com

plex

.dat

.str

uctures.

DNP

.als

.sup

ports

.rep

orting

.of.dev

ice

.dat

.att

ributes

.(na

meplate

.info

rmation).

.T10

.and.T10

.sup

port

.a.gen

eric

.32.bit.bit

string

.obj

ect

.who

.pur

pose

.is.le.ope

.for.imp

lementers

.to.de

ne.

•

. T10

.and.T10

.de

.“no

rmalized,”

.“sc

aled,”

.and.“o

ating-point”

.dat

.obj

ects

.as.di

erent

.kin

of.ana

log

.obj

ects.

.Eac

.of.the.thr

.typ

.als

.has.sep

arate

.set

point

.com

mand

.typ

es.

.Nor

malized

and.sca

led

.are.bot

.16.bit.2’s.com

plement

.int

egers

.and.oa

ting-point

.use

.the.32.bit.“sh

ort”

.for

mat

de

ned

.in.IEE

.754

.For.the.int

eger

.for

mats,

.nor

malized

.dat

.rep

resents

.the.val

ues

.−1.

.to.+1.

0–2

−15

whi

.sca

led

.dat

.rep

resents

.the.val

ues

.−32

768

.to.+32

767.

.Bot

.mus

.be.“sc

aled”

.bef

ore

.tra

nsmission

and.ae

.rec

eption,

.but.by.di

erent

.sca

ling

.fac

tors.

. er

.is.an.imp

lication

.in.the.sta

ndard

.tha

.the.

sca

ling

.fac

tors

.use

.for.the.sca

led

.val

ues

.are.alw

ays

.a.fac

tor

.of.10.(e.

g.,

.0.0

01,

.0.0

.0.1

.1,.10,.100

.etc

and.thi

.sim

plistic

.app

roach

.see

.to.be.com

monly

.use

.Dev

ices

.typ

ically

.onl

.sup

port

.eit

her

.the.

nor

malized

.or.the.sca

led

.for

mat,

.lead

ing

.to.som

.int

eroperability

.iss

ues.

. e.nor

malized

.for

mat

see

.to.be.sli

ghtly

.mor

.com

monly

.use

.tha

.the.sca

led

.for

mat.

.DNP

.trea

.16.bit.int

eger,

.32.bit.

int

eger,

.32.bit.oa

ting-point,

.and.64.bit.oa

ting-point

.as.alt

ernate

.mes

sage

.for

mats

.for.rep

orting

.the.

sam

.obj

ect.

. e.for

mat

.tha

.is.use

.sho

uld

.be.cho

sen

.to.sui

.the.dat

. e.int

eger

.for

mats

.can.be.

sca

led

.as.nee

ded,

.wit

.lin

ear

.sca

ling

.(Y =

AX + B)

.bei

.com

mon.

58-8 Industrial Communication Systems

•. DNP3.permits.the.use.of.“unsolicited.reporting”.on.any.channel.where.the.devices.are.able.to.detect.

channel.activity.in.order.to.avoid.collisions..In.this.mode.of.reporting,.an.outstation.can.send.an.

event.notication.to.a.master.station.without.being.polled.. e.approximately.equivalent.reporting.

mode.for.T101.requires.the.use.of.the.balanced.data.link.rules.and.needs.a.dedicated.point-to-point.

full-duplex.link.between.the.master.station.and.each.outstation.so.that.either.device.is.permitted.

to.transmit.at.any.time.with.no.possibility.of.message.collision..As.will.be.noted.in.Figure.58.2,.the.

number.of.messages.is.the.same.in.balanced.and.unbalanced.modes,.with.the.same.application.layer.

data.being.transferred.in.both.modes.. e.order.and.content.of.the.“link.layer”.messages.diers.

slightly.between.the.two.modes..In.DNP3,.the.use.of.unsolicited.reporting.removes.the.periodic.

polling.for.events,.reducing.the.number.of.messages.as.shown.in.Figure.58.3.

Due

.to.the.limitation.of.a.single.data.type.per.message.and.a.single.COT.per.message,.most.command.

sequences.in.T101.and.T104.require.many.message.transactions..In.T101,.each.transaction.requires.that.

a.message.be.sent.in.each.direction..For.example,.the.two-pass.control.command.on.a.T101.link.shown.

in.Figure.58.2.typically.involves.12.messages.

.equivalent.transaction.for.DNP3.is.shown.in.Figure.58.3,.requiring.that.seven.messages.are.

sent.in.systems.where.the.master.polls.the.outstations,.or.six.messages.if.unsolicited.reporting.is.used..

Similar.distinctions.between.the.protocols.occur.for.most.kinds.of.transactions.

When

.operating.over.TCP/IP,.the.dierence.between.T104.and.DNP3.is.less.pronounced.and.more.

dicult.to.evaluate..For.some.transactions,.T104.will.be.more.ecient.when.it.is.able.to.send.a.stream.

of.information.frames.and.receive.a.single.conrmation.for.the.set.of.frames.(equivalent.to.removing.

Unbalanced data link

Balanced data link

Select control ACT Select control ACT

ACK ACK

Class poll Select control ACTCON

Select control ACTCON ACK

Execute control ACT Execute control ACT

ACK ACK

Class poll Execute control ACTCON

Execute control ACTCON ACK

Class poll Data change

Data change ACK

Class poll Control ACTTERM

Control ACTTERM ACK

FIGURE 58.2 T101.Two-pass.command.sequence.

Polled operation

Unsolicited operation

Select request

Select response

Execute request

Execute response

Read events

Response with data update

Unsolicited data update

Confirm

FIGURE 58.3 DNP3.Two-pass.command.sequence.

DNP3 and IEC 60870-5 58-9

all.except.the.last.ACK.from.the.right-hand.column.of.Figure.58.2)..Associated.with.this.sequence,.

the

.wil

.als

.be.two.or.may

.mor

.TCP

/IP

.con

rmation

.fra

mes.

.In.DNP

.the.sam

.fun

ction

.mig

be.per

formed

.wit

.two.or.thr

.DNP

.mes

sages

.(de

pending

.if.uns

olicited

.rep

orting

.is.use

.and.two.

or.thr

.TCP

/IP

.con

rmation

.fra

mes.

.If.lar

ger

.amo

unts

.of.dat

.are.inv

olved,

.the.numb

.of.DNP

.and.

T10

.me

ssages

.wi

.in

crease.

references

. 1.. IEC. 60870-5-101. Ed.. 2,. Telecontrol. Equipment. and. System—Part. 5:. Transmission. protocols—

Section

. 101:. Com

panion

. sta

ndard

. for. basic. Tele

control

. tas

ks,

. Int

ernational

. Elec

trotechnical

Commi

ssion,

.2002;.ww

w.iec.ch

. 2.. IEC. 60870-5-104. Ed.. 2,. Tele

control

. equi

pment

. and. system

s—Part

. 5:. Tran

smission

. pro

tocols—

Section

.104:.Netw

ork

.access.for.IEC.60870-5-101.using.sta

ndard

.tran

sport

.pro

les,

.Int

ernational

Elec

trotechnical

.Co

mmission,

.2005,.ww

w.iec.ch

. 3.. DNP3.Sp

ecication,

.Ver

.2,.vv

.1–8,.DNP.Us

ers

.Gr

oup

.2007–2009;.ww

w.dnp.org

. 4.. Leiv

.E..and.Newt

on,

.C.,.Mor

.tha

.80%.of.glob

.uti

lity

.resp

ondents

.cla

.to.hav

.subs

tation

aut

omation

.and.integ

ration

.prog

rams

.underwa

.New

ton-Evans Research Company Market Trends

Digest,

.28,.2–4,.2nd.Qu

arter

.2006.